Bob's Knobs

Hand-Adjustable Collimation

The change is simple and the practical difference is large: collimation you will actually perform when needed rather than postpone.

• Direct replacement screws: Thumbscrews with the same thread and length as the originals, so nothing about the optical assembly changes except how you turn them.
• Model-specific sets: Thread size, length and screw count vary between manufacturers and production eras, so the set must match the telescope.
• Schmidt-Cassegrain secondaries: The most common application, replacing the three small hex screws in the secondary holder.
• Newtonian applications: Sets for secondary holders and primary cells on reflectors, removing tools from the collimation process there too.
• No tools in the dark: The real benefit is being able to adjust while looking through the eyepiece, which is the only way to collimate accurately on a star.
• Reversibility: The original screws can be reinstalled at any time, so the change is not permanent.

Why Choose David Astro for Bob's Knobs

Identification is the whole difficulty, since a set for the wrong model will not thread correctly.

• Model and era identified: Secondary assemblies changed over the years within the same product name. We match by model and approximate age rather than by name alone.
• Collimation technique explained: We walk through star collimation procedure, since the knobs make the adjustment easy but not the judgement.
• Honest about necessity: If your telescope holds collimation well and rarely needs adjustment, we will say the benefit is modest.
• Authorized dealer: Genuine products with manufacturer warranty, in Canadian stock.
• Ships from Canada: No duties or brokerage fees for Canadian buyers.

Bob's Knobs in Canada — Frequently Asked Questions

Which set fits my telescope?

It depends on make, model and production era, since secondary assemblies changed over time. Tell us all three and we will identify the correct set.

Is it safe to remove the factory screws?

Yes, if done one at a time so the secondary never loosens. Replace each screw before removing the next, and collimation will barely shift during the change.

Will this affect my warranty?

Changing collimation screws is a reversible user adjustment on most telescopes, but if you have concerns, ask us and we will check the manufacturer's position for your model.

How often should I collimate an SCT?

Check on a star occasionally and after any rough transport. A Schmidt-Cassegrain holds collimation well, but small errors visibly soften planetary detail at high magnification.

Collimating without tools?

Tell us your telescope model and age and we will identify the set. Ships from Canada.